True, no manufacturer is held responsible for the criminal use of their legal products, unless it can be shown that they knowingly or negligently sold the products to criminals. What makes gun manufacturers different is that in their case, this is spelled out in positive law, a law that Bernie Sanders supported.

Hillary Clinton was giving a dog whistle to members of the anti-gun movement, who would have understood she was referring to the Protection of Lawful Commerce in Arms Act.

Based on the exceptions written into the PLCAA, I don’t think it bars reasonable lawsuits against gun manufacturers or dealers. The significance of the issue in the context of the Democratic Presidential debate is that it shows Bernie Sanders has more sympathy for gun owners and gun manufacturers than Hillary Clinton does.